Deletion of individual muscles alters rat walking-track parameters

Rat walking-track analysis has been employed extensively to quantify motor recovery in studies of hindlimb nerve injury and repair. In order to clarify the relationship between individual print measurements and the function of specific hindlimb muscles, 40 young adult rats were assigned to one of five groups (n = 8/group) in which specific deletions of motors were created as follows: Group 1--division of the tendon of insertion of the gastrocnemius, soleus, and plantaris muscles (GSP); Group 2--division of the extensor digitorum longus muscles tendons of insertion (EDL); Group 3--division of the extensor hallicus longus muscle tendon of insertion (EHL); Group 4--division of the tibialis anterior muscle tendon of insertion (TA); or Group 5--division of the tibial nerve at the ankle (TNA). Parameters for print length (PL), intermediate toe spread (IS), and total toe spread (TS) were calculated from walking tracks recorded before and again five days after deletion of the motors. Specific, predictable patterns of change in footprint parameters were observed for each group. It was concluded that triceps surae and tibialis anterior muscle function directly affects print length; EHL function directly influences total toe spread; and EDL function is directly related to intermediary toe spread. These data demonstrate a direct relationship between individual print measurements and the function of individual rat hindlimb muscles.